Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$128.77	7.413%	$138.3157	$138.32	$138.30	$138.30
Purchase #2	$124.36	12.168%	$139.4921	$139.49	$139.50	$139.50
Purchase #3	$206.39	7.707%	$222.2965	$222.30	$222.30	$222.30
Purchase #4	$127.64	11.345%	$142.1208	$142.12	$142.10	$142.10
Purchase #5	$177.37	3.171%	$182.9944	$182.99	$183.00	$183.00
Purchase #6	$31.56	6.510%	$33.6146	$33.61	$33.60	$33.60
Purchase #7	$179.39	4.386%	$187.258	$187.26	$187.25	$187.30
7 purchase totals =	$975.48		$1,046.0921	$1,046.09	$1,046.05	$1,046.10